A Big-Name Index Is No. 2 in Returns

The Russell 2000 Trails the S&P SmallCap 600 Over Multiple Periods

The lineup of stocks in the Russell 2000 small-stock index—and all the index funds that track it—gets an annual tweaking this month. One thing that may not change: the venerable benchmark's lagging performance versus a younger rival.

For tracking small-company stocks, the 30-year old Russell 2000 is the go-to metric for most investors. But there's another game in town, and it has often chalked up better total returns than the Russell: the S&P SmallCap 600. Since its launch, the S&P 600 has beaten the Russell...